1. Field of the Invention
The present disclosure generally relates to detection of melamine contaminants in food and feed samples. More particularly, the disclosure generally relates to systems and methods for using a microbial enzyme to hydrolyze melamine to ammeline and ammonia. The produced ammonia is detected and used to assess the presence and amount of melamine in a sample.
2. Description of the Relevant Art
Melamine contamination of food and feed has recently been recognized as a real threat to the global food supply. Melamine is a common industrial chemical with many legitimate commercial uses in the production of hard plastics, tiling, flame retardants, air filters and other products. However it is toxic and should never be added to food. When melamine is ingested it can cause severe kidney damage which is sometimes fatal. Unfortunately, because of its low price, wide availability and high nitrogen content, melamine has been illegally added to food and feed to increase the apparent protein content. This practice is especially common in, for example, baby formula, milk, milk powder and animal feed. Melamine is a very stable substance and when added to raw materials such as milk powder or animal feed it can accumulate in a wide variety of meats and manufactured food items. Melamine has been found in a wide variety of food types, so testing needs have increased recently.
Currently melamine food testing is performed using: 1) immunoassay (ELISA) tests; 2) mass spectrometry; or 3) HPLC. While these proven methods have worked well in the past, they have significant limitations. Mass spectrometry is very expensive and time consuming. Mass spectrometry requires extensive sample preparation procedures, sophisticated instrumentation, and/or highly skilled analysts. In addition, typically each instrument can only test one sample at a time. The same is typically true for HPLC based methods for melamine detection. For reasons of cost and throughput, both mass spectrometry and HPLC are best suited towards very accurate testing of a limited number of samples. In contrast, antibody-based ELISA methods are often a robust and cost-effective alternative to mass spectrometry and HPLC based detection techniques. ELISA techniques are inexpensive and can test multiple samples at once which make them preferable to the other methods for screening applications; especially for large molecular weight analytes. In spite of these qualities ELISA methods have their own set of limitations. ELISA methods typically require multiple incubations and wash steps. Also, as an antibody-based technique, ELISA tests often do not work well to detect low molecular weight analytes like melamine (MW=126). The practical limitations of the currently available techniques severely impede their capacity to monitor the immense volume and variety of food samples currently under scrutiny. It would be highly desirable to develop a method for melamine detection which does not suffer from these limitations.